1. Field of the Invention
The present invention relates to a smart entry system that includes a portable device and a vehicle-side unit communicating with each other.
2. Description of the Related Art
JP-A-10-59131 discloses a smart entry system including a vehicle-side unit and a portable device. The vehicle-side unit and the portable device communicate with each other when a switch disposed at a door handle of a vehicle door is operated. When the vehicle-side unit receives a normal response signal from the portable device, the vehicle-side unit locks the vehicle door.
In the above-described smart entry system, the vehicle-side unit outputs a low-power confirmation signal and a high-power confirmation signal so as to prevent that the portable device is left in a vehicle compartment. The portable device has a receiving area of the low-power confirmation signal set to be substantially equal to the vehicle compartment. Thus, when the vehicle-side unit receives a response signal from the portable device in response to the low-power confirmation signal, the vehicle-side unit determines that the portable device is left in the vehicle compartment. In this case, the vehicle-side unit does not lock the vehicle door and warns a user of the vehicle.
When vehicle-side unit does not receive a response signal to the low-power confirmation signal, the vehicle-side unit transmits the high-power confirmation signal. The portable device has a receiving area of the high-power confirmation signal set to include a predetermined area around the vehicle. When the vehicle-side unit receives a response signal from the portable device in response to the high-power confirmation signal, the vehicle-side unit determines that a user having the portable device is outside of the vehicle.
In the smart entry system, a plurality of the portable devices may be provided so that a plurality of users can use the vehicle. When a plurality of the portable devices is provided, there is a possibility that a user having one of the portable devices gets out of the vehicle and another one of the portable devices is left in the vehicle compartment. In this case, even if the user operates the switch at the door handle so as to lock the vehicle door, the vehicle door may be not locked and a warning may be generated so as to prevent a theft of the vehicle using the portable device left in the vehicle.
In the conventional smart entry system, a mechanical key is provided so that a use can lock and unlock the vehicle door even when a battery of the portable device runs out. In addition, the conventional smart entry system may include wireless lock function and a wireless unlock function. When the smart entry system includes the wireless lock function and the wireless unlock function, a one-way communication from the portable device to the vehicle-side unit is performed when a user operates a lock switch or an unlock switch disposed at the portable device, and thereby the vehicle door is locked or unlocked.
When the vehicle door is locked using the mechanical key or the wireless lock function, the vehicle door can be locked even when the portable device is left in the vehicle compartment. Thus, the portable device may be locked in the vehicle compartment.
In the smart entry system, a request signal is periodically transmitted to an exterior communication area provided at an outside of the vehicle so as to detect that a user having the portable device approaches the vehicle. When the portable device is in the communication area, the portable device transmits a response signal to the request signal. The vehicle-side unit detects that a user having the portable device approaches the vehicle and the vehicle-side unit unlocks the vehicle door when a touch sensor detects that the user operates the door handle.
Electric wave for providing the exterior communication area may enter the vehicle compartment and the portable device left in the vehicle compartment may transmit a response signal to the request signal for providing the exterior communication area. In this case, a person without the portable device can unlock the vehicle door. In addition, when the portable device left in the vehicle compartment continue to transmit the response signal in response to the request signal which is periodically transmitted, a battery of the portable device may be wasted. Thus, in the conventional entry system, when the vehicle door is locked, a request signal is transmitted to an interior communication area provided in the vehicle compartment and the vehicle-side unit determines whether the portable device is left in the vehicle compartment based on existence or nonexistence of a response signal from the portable device. When the vehicle-side unit determines that the portable device is left in the vehicle compartment, the vehicle-side unit stops transmitting the request signal for providing the exterior communication area so that the person without the portable device cannot unlock the vehicle door.
When the vehicle-side unit completely stops transmitting the request signal for providing the exterior communication area, even when a user has a portable device other than the portable device left in the vehicle compartment, the user cannot unlock the vehicle door using the smart entry system.